Apparatuses, methods and computer programs for locating mobile devices by using photoacoustically-generated audio signals

ABSTRACT

Examples of the disclosure relate to apparatus (101) for positioning mobile devices (105). The apparatus (101) comprises means for: obtaining a time of arrival of at least one audio signal (131) at a mobile device (105), wherein the audio signal (131) is generated with a photoacoustic effect; and using the time of the arrival of the audio signal (131) to estimate a location of the mobile device (105).

TECHNOLOGICAL FIELD

Examples of the disclosure relate to apparatus, methods and computerprograms for locating mobile devices. Some relate to apparatus, methodsand computer programs for locating mobile devices in indoor locations.

BACKGROUND

Systems for locating mobile devices can be used in a variety ofapplications such as communications or for tracking mobile devices asthey move through a warehouse or factory or any other applications inwhich it is useful to know the position of a mobile device.

BRIEF SUMMARY

According to various, but not necessarily all, examples of thedisclosure there is provided an apparatus comprising means for:obtaining a time of arrival of at least one audio signal at a mobiledevice, wherein the audio signal is generated with a photoacousticeffect; and using the time of the arrival of the audio signal toestimate a location of the mobile device.

The audio signal may be generated with a photoacoustic effect by a lightsource at a known location.

The light source may comprise a coating of photoacoustic materialprovided, at least partially, around the light source.

The light source may be coupled to a modulator for modulating intensityof light emitted by the light source.

The audio signal may comprise a predetermined waveform.

The audio signal may have a frequency outside a threshold of humanhearing.

The means may also be for detecting a light signal wherein the lightsignal is generated from the light source that also generates the audiosignal.

The means may also be for using the light signal to synchronise timingbetween the apparatus and the light source.

The means may also be for obtaining the time of arrival of a pluralityof audio signals at a mobile device, wherein the plurality of audiosignals are generated from a plurality of light sources using thephotoacoustic effect at a plurality of known locations.

The plurality of light sources may be synchronised over a network.

According to various, but not necessarily all, examples of thedisclosure there is provided an imaging device comprising at least oneprocessor; and at least one memory including computer program code, theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus at least to perform:obtaining a time of arrival of at least one audio signal at a mobiledevice, wherein the audio signal is generated with a photoacousticeffect; and using the time of arrival of the audio signal to estimate alocation of the mobile device.

According to various, but not necessarily all, examples of thedisclosure there is provided a method comprising: obtaining a time ofarrival of at least one audio signal at a mobile device, wherein theaudio signal is generated with a photoacoustic effect; and using thetime of arrival of the audio signal to estimate a location of the mobiledevice.

According to various, but not necessarily all, examples of thedisclosure there is provided a computer program comprising computerprogram instructions that, when executed by processing circuitry, cause:obtaining a time of arrival of at least one audio signal at a mobiledevice, wherein the audio signal is generated with a photoacousticeffect; and using the time of arrival of the audio signal to estimate alocation of the mobile device.

According to various, but not necessarily all, examples of thedisclosure there is provided a mobile apparatus comprising means for:detecting an audio signal wherein the audio signal is generated with aphotoacoustic effect at a known location; and enabling the detectedaudio signal to be used to estimate a location of the mobile apparatus.

According to various, but not necessarily all, examples of thedisclosure there is provided a light source apparatus comprising; alight source configured to generate a light signal; a modulatorconfigured to modulate intensity of light emitted by the light source;and a coating of photoacoustic material provided, at least partially,around the light source so that audio signal generated using thephotoacoustic material can be used to estimate the location of a mobileapparatus.

The modulator may be configured to control the intensity of lightemitted by the light source so that the audio signal generated using thephotoacoustic material comprises a predetermined waveform.

The waveform may have a frequency outside threshold of human hearing.

The audio signal may comprise an audio pulse.

According to various, but not necessarily all, examples of thedisclosure there is provided a light source apparatus is synchronisedwith one or more other light source apparatus.

According to various, but not necessarily all, examples of thedisclosure there is provided a system comprising a plurality of lightsource apparatus as described.

The system may comprise means for: obtaining a time of arrival of aplurality of audio signals at a mobile device, wherein the audio signalsis generated from the plurality light source apparatus with thephotoacoustic effect at a plurality of known locations; and using thetime of arrival of the plurality of audio signals to estimate a locationof the mobile device.

BRIEF DESCRIPTION

Some examples will now be described with reference to the accompanyingdrawings in which:

FIG. 1 shows an example system;

FIG. 2 shows an example light source apparatus;

FIG. 3 shows an example light source apparatus;

FIG. 4 shows an example of the disclosure in use;

FIG. 5 shows an example of the disclosure in use;

FIG. 6 shows an example of the disclosure in use;

FIG. 7 shows an example apparatus; and

FIG. 8 shows an example method.

DETAILED DESCRIPTION

Examples of the disclosure relate to systems 101 that enable locationsof mobile devices 105 to be estimated. FIG. 1 schematically shows anexample system 101 that can be used to implement examples of thedisclosure. The system 101 shown in FIG. 1 comprises a plurality oflight source apparatus 103, one or more mobile devices 105 and aprocessing device 107. It is to be appreciated that in someimplementations the systems 101 could comprise additional componentsthat are not shown in FIG. 1 .

The light source apparatus 103 can comprise any apparatus that areconfigured to generate an audio signal 131 with a photoacoustic effect.In the example shown in FIG. 1 the light source apparatus 103 comprise alight source 111 and a coating of photoacoustic material 113 provided,at least partially, around the light source 111.

The light source 111 can be a light bulb, a light emitting diode, ahalogen lamp or any other suitable means for generating light. The lightgenerated by the light source 111 can comprise electromagnetic radiationin the visible portion of the spectrum. For instance, the light source111 can generate light with a wavelength between 400 nm and 700 nm. Insome examples the light source 111 can generate light outside of thevisible portion of the spectrum, for example the light source couldgenerate infra-red or ultra-violet light.

The light from the light source 111 can be used to provide illuminationfor the area in which the system 101 is located. For example, the lightsources 111 can provide visible light that can illuminate a room orother environment. This could enable the light source apparatus 111 toprovide dual functionality of enabling the estimate of the locations ofthe mobile devices 105 and also illuminating the area of the system 101.

A coating of photoacoustic material 113 is provided around the lightsource 111 so that at least some of the light generated by the lightsource 111 is incident on the photoacoustic material 113. Thephotoacoustic material 113 can comprise any optically absorptivematerial that can generate an audio signal 131 when light is incident onit. The photoacoustic material 113 can comprise a black material such ascharcoal or a stored sample of a greenhouse gas or any other suitabletype of material.

When the light source apparatus 103 is in use the light source 111generates light and the photoacoustic material 113 is heated by theincident light from the light source 111.

This heating causes expansion of the air around the photoacousticmaterial 113 which generates the audio signal 113. The audio signal 131comprises a pressure wave that is transmitted through the air or anyother suitable medium. In some examples the audio signal 131 could havea frequency that is outside of the range of normal human hearing. Forexample, the audio signal 131 could have a frequency in the range 20 kHzto 24 kHz.

In the example shown in FIG. 1 the light source apparatus 103 alsocomprises a modulator 109. The modulator 109 comprises means formodulating the intensity of light emitted by the light source 111. Themodulator 109 can apply a predetermined waveform to the intensity of thelight emitted by the light source 111. The applied waveforms cancomprise any suitable waveforms that can be used to generate an audiosignal. In some examples the waveforms could comprise sine waves, shortpulses, or any other suitable types of waveforms. The waveforms that canbe used can be stored in a memory that is accessible by the modulator109.

The modulator 109 can be configured to control the power provided to thelight source 111 in accordance with the predetermined waveform. Thiscontrols the intensity of light emitted by the light source 111 and soin turn controls the heating of the photoacoustic material 113 caused bythe light. This enables an audio signal 131 with a predefined waveformto be generated by the light source apparatus 103.

In examples of the disclosure the light source apparatus 103 has a knownposition within the system 101. In some examples the light sourceapparatus 103 could have a fixed position. For example, it can be fixedto a ceiling or wall. In other examples the light source apparatus 103could be moveable but the position of the light source could bedetermined by any suitable positioning means so that the location of themobile devices 105 can be estimated from this known location.

In the example shown in FIG. 1 the system 101 comprises a plurality oflight source apparatus 103. The plurality of light source apparatus 103are positioned at different known locations within the area covered bythe system 101. The plurality of light source apparatus 103 eachcomprise a light source 111 and photoacoustic material 113 as describedabove. In the example shown in FIG. 1 each of the light source apparatus103 each comprise a modulator 109 that is configured to modulate each ofthe individual light sources 111. In some examples a central modulator109 could be configured to modulate a plurality of the light sources111.

Where the system comprises a plurality of light source apparatus 103 theplurality of light source apparatus 103 can synchronized so that thetiming of audio signals 131 generated by the light source apparatus 103are emitted at known times. In some examples the audio signals 131 canbe emitted at the same time from each of the light source apparatus 103.In other examples the audio signals 131 can be emitted at predeterminedintervals.

The plurality of light source apparatus 103 can be synchronized usingany suitable means. For instance, the light source apparatus 103 can bepart of a wired or wireless communications network.

The system 101 shown in FIG. 1 also comprises a mobile device 105. Onlyone mobile device 105 is shown in FIG. 1 however it is to be appreciatedthat any number of mobile devices could be provided within the system101 in other examples of the disclosure.

The mobile device 105 can be any device that can move within the areacovered by the system 101. In some examples the mobile device 105 couldbe a personal communications device such as a mobile phone or a wearabledevice such as a smart watch. In other examples the mobile devices 105could be tags or other identifiers that can be attached to objects. Forexample, tracking devices could be attached to objects in a factory orwarehouse and used to monitor the positions of the objects as they movethrough the factory or warehouse. In some examples the mobile devices105 could comprise wearable devices such as jackets or hats thatcomprise circuitry, such as the circuitry shown in FIG. 1 , that enablesthe wearable device to be located using examples of the disclosure. Thiscould enable a person wearing such mobile devices 105 to be located.

In the example shown in FIG. 1 the mobile device 105 comprises an audiosensor 121 and a processor 123. It is to be appreciated that only thecomponents relevant for this disclosure are shown in FIG. 1 and that themobile device 105 would also comprise additional components that are notshown in FIG. 1 . For instance, the mobile device 105 could comprisetransceiver circuitry that enables the mobile device to communicate in awireless network.

The audio sensor 121 comprises any means that can be configured to sensethe audio signal 131. The audio sensor 121 can comprise one or moremicrophones. The audio sensor 121 can be configured to sense the audiosignal 131 and provide an electrical output signal in response to thedetection of the audio signal 131.

The audio sensor 121 is coupled to the processor 123 so that the outputof the audio sensor 121 is provided to the processor 123. The processor123 can be configured to analyse the output signal from the audio sensor121 to determine whether or not the sensed audio signal 131 correspondsto the predetermined waveform. If it is determined that the audio signal131 has the predetermined waveform then it can be determined to be anaudio signal from one of the light source apparatus 105. The processor123 is configured to estimate the time of arrival of the audio signal131 and enable this to be used to estimate the location of the mobiledevice 105.

In the example shown in FIG. 1 the system 101 comprises a processingdevice 107. The processing device 107 is configured to use the estimatedtime of arrival of the audio signal 131 at the mobile device 105 toestimate a position of the mobile device 105. The processing device 107comprises a processor 123 that can be configured to perform theprocessing to estimate the position of the mobile device 105. It is tobe appreciated that the processing device 107 could also compriseadditional components that are not shown in FIG. 1 such as transceivercircuitry for enabling communication with the other components of thesystem 101.

In the example shown in FIG. 1 the processing device 107 is providedseparately to both the mobile device 105 and the light source apparatus103. In this example the processing device 107 is a separate device thatcan communicate with the mobile device 105 and the light sourceapparatus 103 using a communication network. This can enable the mobiledevice 105 to provide information, such as the time of arrival of anaudio signal 131 at the mobile device 105, to the processing device 107.

The processing device 107 can also be configured to determine the timethat the light was emitted by the light source 111. In some examples theprocessing device 107 can comprise a light sensor that can be configuredto detect the modulation of light from the light source 111. As thespeed of light is so much faster than the speed of sound the modulationof the light can be detected instantaneously. This enables theprocessing device to determine to as the time at which the light isdetected. In other examples the light sources 111 could be synchronizedand the timings used for this synchronization could be provided to theprocessing device 107 via a communications network or any other suitablemeans. In such cases the processing device 107 could use this receivedinformation to determine t₀.

Once the processing device has determined to the timing of the audiosignals can then be measured as a delay relative to t₀.

For instance, if the audio signal 131 is received at time t₁ then thedistance d between the light source apparatus 103 and the mobile device105 is given by

d=c(t ₁ −t ₀)

where c is the speed of sound for the audio signal. The speed of soundfor the audio signal can be adjusted to take into account parameterssuch as temperature and humidity.

In the example shown in FIG. 1 only one audio signal 131 from one lightsource apparatus 103 is shown. It is to be appreciated that in otherexamples a plurality of audio signals 131 from a plurality of differentlight source apparatus 103 could be used. This can enable a moreaccurate location for the mobile device 103 to be determined. Anysuitable processes, such as multilateration algorithms, can be used toestimate the position of the mobile device 105.

It is to be appreciated that variations of the system 101 shown in FIG.1 could be used in other examples of the disclosure. For instance, inother examples the processor 123 of the mobile device 105 could beconfigured to estimate a position of the mobile device 105. In suchexamples the processing device 107 might not be needed as the relevantprocessing could be performed by the processor 123 of the mobile device105.

In other examples one or more of the light source apparatus 103 could beconfigured to perform the processing for estimating the location of themobile device 105. In such examples one or more of the light sourceapparatus 103 could be configured to communicate with the mobile device105 and enable the light source apparatus 103 to obtain the informationrelating to the timing of the receipt of the audio signals 131. Thisinformation can then be used to estimate the position of the mobiledevice 105.

FIG. 2 shows an example light source apparatus 103 that can be used insome examples of the disclosure.

In this example the light source apparatus 103 comprises a light bulb201. The light bulb 201 comprises a filament 203 that provides a lightsource 111 when a current is passed through it. In other examples meanssuch as an LED, or any other suitable means, could be provided insteadof the filament 203.

The filament 203 is provided within a casing 205 of the light bulb 201.The casing 205 can be formed from glass or any other suitable material.The casing 205 is transparent to enable the light generated by the lightsource 111 to pass through the casing 205.

A coating of photoacoustic material 113 is provided on the casing 205 ofthe light bulb 201. The photoacoustic material 113 can comprise charcoalor any other suitable 30 material.

The photoacoustic material 113 is provided on the casing 205 of thelight bulb 201 so that light emitted from the light source 111 isincident on the photoacoustic material 113 and can be absorbed by thephotoacoustic material 113.

The photoacoustic material 113 is provided to partially cover the casing205 of the light bulb so that only part of the light emitted by thelight source 111 is absorbed by the photoacoustic material 113. Thelight that is not incident on the photoacoustic material 113 can beemitted through the casing 205. This can enable the light that is notabsorbed by the photoacoustic material 113 to be used to illuminate thearea in which the system 101 is located. The amount of photoacousticmaterial 113 that is provided on the casing 205 of the light bulb 201can be selected so that there is enough photoacoustic material 113 toenable a detectable audio signal to be produced but avoids too muchlight being absorbed so that a user does not notice any fluctuation inlight levels.

The photoacoustic material 113 generates sound via the photoacousticeffect in accordance with the following equation:

$p = {\frac{\beta}{\kappa\rho C_{v}}A_{e}}$

Where p is the acoustic pressure generated, κ is the compressibility ofthe absorptive material sample, p is the absorptive material density,C_(v) is the specific heat capacity of the absorptive material atconstant volume, β is the thermal expansion coefficient of theabsorptive material and A_(e) is the optical energy absorbed per unitvolume.

The rest of the optical energy that is not absorbed by the photoacousticmaterial 113 propagates through the casing 205 and into the surroundingenvironment to provide light for the area around the light sourceapparatus 103.

In the example shown in FIG. 2 the photoacoustic material 113 isprovided in a plurality of bands around the casing 205 of the bulb 201.Spacings are provided between the bands to enable light to pass throughthe casing 205. Other patterns for the photoacoustic material 113 couldbe used in other examples of the disclosure.

In the example shown in FIG. 2 the photoacoustic material 113 isprovided in a symmetric pattern so that the audio signal 131 generatedby the photoacoustic material 113 is emitted equally in all directions.In other examples an asymmetric pattern could be used.

The light source apparatus 103 also compares a modulator 109. Themodulator 109 can comprise any circuitry that enables the intensity ofthe light emitted by the light source 111 to be controlled. Themodulator 109 can comprise memory circuitry for storing predeterminedwaveforms that can be used to modulate the intensity of light emitted bythe light sources. In some examples the modulator 109 can comprisetiming circuitry which is configured to enable the timing of themodulations to be synchronized with one or more other light sourceapparatus 103.

In the example shown in FIG. 2 the modulator 109 is provided around thebase of the light bulb 201. This can enable the light bulb 201 to beused in standard light fittings without any modification to the lightfittings or the other circuitry coupled to the light fittings.

FIG. 3 shows a cross section of another example light source apparatus103 that could be used in examples of the disclosure.

In this example the photoacoustic material 113 is provided on a cover309 of a light fitting. The light source apparatus 103 comprises a lightsource 111. The light source 111 could be a bulb, one or more lightemitting diodes or any other suitable type of light source 111. Thelight source 111 in this example could be a standard bulb or lightemitting diode arrangement that has not been modified specifically foruse in this system 111 because the photoacoustic material 113 isprovided on the cover 309 of the light fitting rather than on the lightsource 111 itself.

In the example shown in FIG. 3 the cover 309 is provided around thelight source 111. The cover 309 comprises alternating portions of anoptically transparent material 301 and a photoacoustic material 113. Theportions of optically transparent material 301 and photoacousticmaterial 113 could be provided in a checkerboard arrangement or anyother suitable pattern. The photoacoustic material 113 can comprisecharcoal or any other suitable material. In the example shown in FIG. 3the photoacoustic material 113 is provided as part of the cover 309 sothat the photoacoustic material 113 extends through the thickness of thecover 309. In other examples the photoacoustic material 113 could beprovided as a coating on the surface of portions of the cover 309.

The optically transparent material 301 can comprise any material thatenables light generated by the light source 111 to pass through thecover 309. The optically transparent material can comprise glass,plastics or any other suitable type of material.

The light source 111 is coupled to circuitry that controls the intensityof the light emitted by the light source 111. In the example shown inFIG. 3 this circuitry is provided separate to the light source 111. Forexample, the circuitry can be provided as part of a communicationsnetwork that can be used to control a plurality of light sources 111.For example, the circuitry could be part of an internet of things or anyother suitable network. This can also enable a standard light source 111to be used within the system 101.

In the example shown in FIG. 3 the circuitry comprises a timing module303. In this example the timing module 303 can be configured to receiveclock information from a network. The clock information can enable aplurality of light source apparatus 103 to be synchronized. The clockinformation can enable the audio signals generated by the light sourceapparatus 103 to be emitted at predetermined times.

The circuitry also comprises an audio signal module 305. The audiosignal module 305 can comprise information relating to the waveform thatis to be applied to the audio signal. For example, the audio signalmodule 305 can store information relating to a predetermined waveformthat is to be applied to the audio signal 131 at the predeterminedtimes.

The circuitry also comprises a power supply 307. In some examples thepower supply 307 can comprise a mains power supply that can be connectedto the light source 111. Other types of power supplies, such asbatteries, could be used in other examples of the disclosure.

The modulator 109 is configured to control the intensity of the powersupplied to the light source 111. The modulator 109 controls theintensity of the power supplied so that a modulated light signal isprovided from the light source 111 which in turn provides a modulatedaudio signal 131 from the photoacoustic material 113.

The modulator 109 uses timing information from the timing module 303 toensure that the modulated light signal is provided at a predeterminedtime. The modulator 109 uses audio signal information from the audiosignal module 305 to ensure that the modulated light signal, andcorresponding audio signal, comprise the predetermined waveform. Theaudio signal could comprise a sequence of ultrasonic chirps or any othersuitable audio signals.

FIG. 4 shows an example system 101 in use. The example system 101comprises a plurality of light source apparatus 103 that comprisephotoacoustic material 113 for generating an audio signal 131 from alight source 111. The plurality of light source apparatus 103 can be asshown in FIG. 2 or 3 or could be any other suitable type of light sourceapparatus 103.

In FIG. 4 the plurality of light source apparatus 103 are providedwithin a room or other indoor environment. The plurality of light sourceapparatus 103 are configured to provide illumination of the room orother indoor environment.

The plurality of light source apparatus 103 are positioned at differentlocations within the room. In the example shown in FIG. 4 the positionsof the light source apparatus 103 can be fixed, known positions. In theexample shown in FIG. 4 the plurality of light source apparatus 103 areprovided on the ceiling of the room. In other examples the plurality oflight source apparatus 103 could be provided on the walls or in anyother suitable location.

The plurality of light source apparatus 103 are connected to a network401. The network can comprise a Li-Fi network or any suitable type ofnetwork that enables the plurality of light source apparatus 103 to besynchronized.

The network 401 can also comprise one or more modulators 109 configuredto control the modulation of the light sources 111 within the pluralityof light source apparatus 103. The modulators 109 can be configured tocontrol the modulation of the light sources 111 at defined times andfrequencies. The modulation of the light sources can be controlled sothat it would not be perceived by users 403 within the area.

The modulators 109 can control the modulation of light so that it can bedetermined which light source apparatus 103 a modulated light signaland/or modulated audio signal 131 originates from. In some examples themodulators 109 can control the plurality of light source apparatus 103so that different light signals are modulated at different times. Insome examples the modulators 109 can control the plurality of lightsource apparatus 103 so that different light signals are modulated withdifferent frequencies.

In the example shown in FIG. 4 a user 403 is in the indoor area coveredby the system 101. The user 403 is using their mobile device 105 whichin this example is a mobile phone. Other types of mobile devices 105could be used in other examples of the disclosure.

The mobile device 105 can be connected to the same network 401 as theplurality of light source apparatus 103. This can enable the mobiledevice 105 to be synchronized in time with the plurality of light sourceapparatus 103.

The system 101 can enable the location of the mobile device 105 to bedetermined. The audio signals 131 from the plurality of light sourceapparatus 103 can be detected by an audio sensor 121 in the mobiledevice 105. The time of arrival of the audio signal 131 at the mobiledevice 105 can be recorded. As the mobile device 105 is part of the samenetwork 401 as the plurality of light source apparatus 103 the time thatthe audio signal 131 was emitted by the light source apparatus 103 isknown. The distance between the mobile device 105 and the light sourceapparatus 103 that emitted the detected audio signal 131 can bedetermined based on the speed of sound. This process can be repeated fora plurality of audio signals 131 from a plurality of different lightsource apparatus 103. A process such as multilateration can be used toestimate the position of the mobile device based on the distancemeasurements.

In some other examples the mobile device 105 might not be connected tothe same network 401 as the light source apparatus 103. In such examplesthe light signal 405 emitted by the light source apparatus 103 could beused to synchronize the mobile device 105 with the light sourceapparatus 103. The speed of light is such that, for the purposes ofestimating the location of the mobile device 105, the light signal canbe considered to be propagated to the mobile device 105 instantaneously.

This system 101 shown in FIG. 4 therefore enables the location of mobiledevices 105 and the users of mobile devices 105 to be located. This canbe useful for communication purposes or for any other suitable purposes.

FIG. 5 shows another example system 101 in use. This system could beused in a factory or warehouse or another suitable environment. Thesystem could enable items to be tracked within a warehouse or factory.

The example system 101 comprises a plurality of light source apparatus103 that comprise photoacoustic material 113 for generating an audiosignal 131 from a light source 111. The plurality of light sourceapparatus 103 can be as shown in FIG. 2 or 3 or could be any othersuitable type of light source apparatus 103.

In FIG. 5 the plurality of light source apparatus 103 can be configuredto provide illumination of the warehouse or factory.

In this example the mobile devices 105 comprise items that are movingthrough the warehouse or factory. Audio sensors 121 can be attached tothe items to enable the audio signals 131 to be detected. In someexamples the mobile devices 105 can also comprise communicationcircuitry that can enable information to be transmitted from the mobiledevice 105 to a network. For example, information relating to the timeof arrival of an audio signal could be transmitted. Or in some examplesthe mobile device 105 can be configured to estimate its own location andprovide this estimate to a network.

In some sections the mobile device 105 can be moved autonomously, forexample the mobile devices 105 can be positioned on conveyor belts 501or could be moved by robotic arms or by any other suitable means. Whenthe mobile devices 105 are being moved autonomously they are being movedwithout any input from a human user 403. In such examples the locationestimates obtained from the system 101 can be used to control theconveyor belts 501 or robotic arms to move the mobile devices 105.

In some sections the mobile device 105 could also be moved manually byone or more users 403. In such sections a user 403 could pick up themobile device 105 and move it to another location. In such examples thepositioning system 101 can be used to track the locations of the variousmobile items.

In the system 101 shown in FIG. 5 both manual and autonomous movement ofthe mobile devices 105 is used. It is to be appreciated that in otherexamples the movement of the mobile deices 105 could be just autonomousor just manual.

FIG. 6 shows another example system 101 in use. This system 101 could beused for improving a conferencing service. In the example shown in FIG.6 the system 101 comprises one light source apparatus 103. It is to beappreciated that a plurality of light source apparatus 103 could be usedin other examples of the system 101.

In this example the system 101 also comprises a plurality of audiotransducers 601. The audio transducers 601 can comprise one or moremicrophones that can be configured to detect audio signals from theusers 403 of the system 101. For example, the microphones can beconfigured to detect speech or other sounds from the users 403. Theaudio transducers 601 could also comprise one or more speakers that areconfigured to provide audio signals for the users 403. For instance,sounds recorded at another location could be transmitted to the system101 via a communications network and played back to the users 403 usingthe speakers.

In this example of the disclosure the light source apparatus 103 can beconfigured so that the audio signal generated by the photoacousticmaterial 113 is outside of the audible range. This can prevent the audiosignal generated by the photoacoustic material 113 from interrupting theuser's 403 speaking or any other audio that might be played back by theaudio transducers.

In the example shown in FIG. 6 a plurality of users 403 are using theconferencing. Each of the user's has a mobile device 105 such as alaptop, mobile phone or tablet computer. The positioning system 101 canbe used to estimate the position of the mobile devices 105 belonging toeach of the users and use that to determine the location of the varioususers 403 in the room.

Once the location of the various users 403 has been estimated this canbe used to control the audio transducers 601. For instance, if it isdetermined that a first user 403 in a first location is talking then thegains of the audio transducers 601 can be controlled so that the firstuser 403 is heard louder than the other users. For example, larger gainscould be provided for the microphones closest to the user 401 who iscurrently speaking. As the other users in the room would be recordedmore quietly this could reduce interruptions from background noisecaused by the other users 403 in the room.

FIG. 7 schematically illustrates an apparatus 701 according to examplesof the disclosure. The apparatus 701 illustrated in FIG. 7 may be a chipor a chip-set. In some examples the apparatus 701 may be provided withindevices such as a mobile device 101 or a processing device 107 withinthe system 101 as shown in FIG. 1 or any other suitable device.

In the example of FIG. 7 the apparatus 701 comprises a controller 703.In the example of FIG. 7 the implementation of the controller 703 may beas controller circuitry. In some examples the controller 703 may beimplemented in hardware alone, have certain aspects in softwareincluding firmware alone or can be a combination of hardware andsoftware (including firmware).

As illustrated in FIG. 7 the controller 703 may be implemented usinginstructions that enable hardware functionality, for example, by usingexecutable instructions of a computer program 709 in a general-purposeor special-purpose processor 123 that may be stored on a computerreadable storage medium (disk, memory etc.) to be executed by such aprocessor 123.

The processor 123 is configured to read from and write to the memory707. The processor 123 may also comprise an output interface via whichdata and/or commands are output by the processor 123 and an inputinterface via which data and/or commands are input to the processor 123.

The memory 707 is configured to store a computer program 709 comprisingcomputer program instructions (computer program code 711) that controlsthe operation of the apparatus 701 when loaded into the processor 123.The computer program instructions, of the computer program 709, providethe logic and routines that enables the apparatus 701 to perform methodssuch as the method illustrated in FIG. 8 . The processor 123 by readingthe memory 707 is able to load and execute the computer program 709.

The apparatus 701 therefore comprises means for: obtaining a time ofarrival of at least one audio signal 131 at a mobile device 105, whereinthe audio signal 131 is generated with a photoacoustic effect; and usingthe time of the arrival of the audio signal 131 to estimate a locationof the mobile device 105.

As illustrated in FIG. 7 the computer program 709 may arrive at theapparatus 701 via any suitable delivery mechanism 705. The deliverymechanism 705 may be, for example, a machine readable medium, acomputer-readable medium, a non-transitory computer-readable storagemedium, a computer program product, a memory device, a record mediumsuch as a Compact Disc Read-Only Memory (CD-ROM) or a Digital VersatileDisc (DVD) or a solid state memory, an article of manufacture thatcomprises or tangibly embodies the computer program 709. The deliverymechanism may be a signal configured to reliably transfer the computerprogram 709. The apparatus 701 may propagate or transmit the computerprogram 709 as a computer data signal. In some examples the computerprogram 709 may be transmitted to the apparatus 701 using a wirelessprotocol such as Bluetooth, Bluetooth Low Energy, Bluetooth Smart,6LoWPan (IP_(v)6 over low power personal area networks) ZigBee, ANT+,near field communication (NFC), Radio frequency identification, wirelesslocal area network (wireless LAN) or any other suitable protocol.

The computer program 709 comprises computer program instructions forcausing an apparatus 701 to perform at least the following: obtaining atime of arrival of at least one audio signal 131 at a mobile device 105,wherein the audio signal 131 is generated with a photoacoustic effect;and using the time of arrival of the audio signal 131 to estimate alocation of the mobile device 105.

The computer program instructions may be comprised in a computer program709, a non-transitory computer readable medium, a computer programproduct, a machine readable medium. In some but not necessarily allexamples, the computer program instructions may be distributed over morethan one computer program 709.

Although the memory 707 is illustrated as a single component/circuitryit may be implemented as one or more separate components/circuitry someor all of which may be integrated/removable and/or may providepermanent/semi-permanent/dynamic/cached storage.

Although the processor 123 is illustrated as a singlecomponent/circuitry it may be implemented as one or more separatecomponents/circuitry some or all of which may be integrated/removable.The processor 123 may be a single core or multi-core processor.

References to “computer-readable storage medium”, “computer programproduct”, “tangibly embodied computer program” etc. or a “controller”,“computer”, “processor” etc. should be understood to encompass not onlycomputers having different architectures such as single/multi-processorarchitectures and sequential (Von Neumann)/parallel architectures butalso specialized circuits such as field-programmable gate arrays (FPGA),application specific circuits (ASIC), signal processing devices andother processing circuitry. References to computer program,instructions, code etc. should be understood to encompass software for aprogrammable processor or firmware such as, for example, theprogrammable content of a hardware device whether instructions for aprocessor, or configuration settings for a fixed-function device, gatearray or programmable logic device etc.

As used in this application, the term “circuitry” may refer to one ormore or all of the following:

-   -   (a) hardware-only circuitry implementations (such as        implementations in only analog and/or digital circuitry) and    -   (b) combinations of hardware circuits and software, such as (as        applicable):        -   (i) a combination of analog and/or digital hardware            circuit(s) with software/firmware and        -   (ii) any portions of hardware processor(s) with software            (including digital signal processor(s)), software, and            memory(ies) that work together to cause an apparatus, such            as a mobile phone or server, to perform various functions            and    -   (c) hardware circuit(s) and or processor(s), such as a        microprocessor(s) or a portion of a microprocessor(s), that        requires software (e.g. firmware) for operation, but the        software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term circuitry also covers an implementation ofmerely a hardware circuit or processor and its (or their) accompanyingsoftware and/or firmware. The term circuitry also covers, for exampleand if applicable to the particular claim element, a baseband integratedcircuit for a mobile device or a similar integrated circuit in a server,a cellular network device, or other computing or network device.

FIG. 8 illustrates an example method. The method could be implementedusing an apparatus 701 as shown in FIG. 7 . The apparatus 701 could beprovided within a mobile device 105 or within a processing device 107 orwithin any other suitable device within the system 101 as shown in FIG.1 .

The method comprises, at block 801, obtaining a time of arrival of atleast one audio signal 131 at a mobile device 105. The audio signal 131is with a photoacoustic effect.

The audio signal can be generated by a light source 111 at a knownlocation that uses a photoacoustic effect. At block 803 the methodcomprises, using the time of arrival of the audio signal 131 to estimatea location of the mobile device 105.

Examples of the disclosure therefore provide a positioning system thatcan be used to estimate the location of mobile devices 105. The lightsources 111 that are used to generate the audio signals can also be usedto provide light for the building or area in which the system 101 islocated. This minimizes the hardware that is needed to implement theexamples of the disclosure as it can be provided by making slightmodifications to existing light fittings.

In some examples of the disclosure the positioning system 101 can beused to replace or augment existing positioning systems such as Lidar orcamera based systems. For example, the location estimates obtained usingthe above described positioning systems 101 could be used to reduce theprocessing requirements of other positioning systems.

The above described examples find application as enabling components of:automotive systems; telecommunication systems; electronic systemsincluding consumer electronic products; distributed computing systems;media systems for generating or rendering media content including audio,visual and audio visual content and mixed, mediated, virtual and/oraugmented reality; personal systems including personal health systems orpersonal fitness systems; navigation systems; user interfaces also knownas human machine interfaces; networks including cellular, non-cellular,and optical networks; ad-hoc networks; the internet; the internet ofthings; virtualized networks; and related software and services.

The term ‘comprise’ is used in this document with an inclusive not anexclusive meaning. That is any reference to X comprising Y indicatesthat X may comprise only one Y or may comprise more than one Y. If it isintended to use ‘comprise’ with an exclusive meaning then it will bemade clear in the context by referring to “comprising only one . . . ”or by using “consisting”.

In this description, reference has been made to various examples. Thedescription of features or functions in relation to an example indicatesthat those features or functions are present in that example. The use ofthe term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the textdenotes, whether explicitly stated or not, that such features orfunctions are present in at least the described example, whetherdescribed as an example or not, and that they can be, but are notnecessarily, present in some of or all other examples. Thus ‘example’,‘for example’, ‘can’ or ‘may’ refers to a particular instance in a classof examples. A property of the instance can be a property of only thatinstance or a property of the class or a property of a sub-class of theclass that includes some but not all of the instances in the class. Itis therefore implicitly disclosed that a feature described withreference to one example but not with reference to another example, canwhere possible be used in that other example as part of a workingcombination but does not necessarily have to be used in that otherexample.

Although examples have been described in the preceding paragraphs withreference to various examples, it should be appreciated thatmodifications to the examples given can be made without departing fromthe scope of the claims. For instance, in some examples the mobiledevice 105 doesn't need to be synchronized with the light sourceapparatus 101. In such examples a direction of arrival of the audiosignal 131 could be determined so that triangulation rather thanmultilateration can be used to estimate the position of the mobiledevice 105. In such examples the mobile device 105 comprises an array ofaudio sensors 121 that are configured to detect the direction of arrivalof the audio signal 131. The audio sensors 121 can be spaced apart onthe mobile device 105 so that the direction of arrival of an audiosignal 131 can be determined from phase and amplitude differencesmeasured by the audio sensors 121. In some examples the audio sensors121 could be configured in a symmetric circular or spherical array sothat the response will be equal for all angles.

Features described in the preceding description may be used incombinations other than the combinations explicitly described above.

Although functions have been described with reference to certainfeatures, those functions may be performable by other features whetherdescribed or not.

Although features have been described with reference to certainexamples, those features may also be present in other examples whetherdescribed or not.

The term ‘a’ or ‘the’ is used in this document with an inclusive not anexclusive meaning. That is any reference to X comprising a/the Yindicates that X may comprise only one Y or may comprise more than one Yunless the context clearly indicates the contrary. If it is intended touse ‘a’ or ‘the’ with an exclusive meaning then it will be made clear inthe context. In some circumstances the use of ‘at least one’ or ‘one ormore’ may be used to emphasis an inclusive meaning but the absence ofthese terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is areference to that feature or (combination of features) itself and alsoto features that achieve substantially the same technical effect(equivalent features). The equivalent features include, for example,features that are variants and achieve substantially the same result insubstantially the same way. The equivalent features include, forexample, features that perform substantially the same function, insubstantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples usingadjectives or adjectival phrases to describe characteristics of theexamples. Such a description of a characteristic in relation to anexample indicates that the characteristic is present in some examplesexactly as described and is present in other examples substantially asdescribed.

Whilst endeavoring in the foregoing specification to draw attention tothose features believed to be of importance it should be understood thatthe Applicant may seek protection via the claims in respect of anypatentable feature or combination of features hereinbefore referred toand/or shown in the drawings whether or not emphasis has been placedthereon.

I/We claim:
 1. An apparatus comprising means for at least one processor;and at least one memory including computer program code, the at leastone memory and the computer program code configured to, with the atleast one processor, cause the apparatus at least to: obtain an emittingtime of at least one audio signal, wherein the at least one audio signalis generated with a photoacoustic effect; obtain a time of arrival ofthe emitted at least one audio signal relation to a mobile device,wherein the emitted audio signal is captured at the mobile device; andestimate a location of the mobile device based on the emitting time andthe time of arrival.
 2. An apparatus as claimed in claim 1, wherein theat least one audio signal is generated with the photoacoustic effect byat least one light source at a known location.
 3. An apparatus asclaimed in claim 2, wherein the at least one light source comprises acoating of photoacoustic material provided, at least partially, aroundthe light source.
 4. An apparatus as claimed in claim 2, wherein the atleast one light source is coupled to a modulator for modulatingintensity of light emitted by the light source.
 5. An apparatus asclaimed in claim 1, the at least one audio signal comprises apredetermined waveform.
 6. An apparatus as claimed in claim 1, whereinthe at least one audio signal has a frequency outside a threshold ofhuman hearing.
 7. An apparatus as claimed in claim 2, wherein theapparatus is caused to detect a light signal, and wherein the lightsignal is generated from the at least one light source that alsogenerates the audio signal.
 8. An apparatus as claimed in claim 7,wherein the means are also for using the light signal apparatus iscaused to synchronise timing between the apparatus and the at least onelight source by using the light signal.
 9. An apparatus as claimed inclaim 1, wherein the apparatus is caused to obtain the time of arrivalof a plurality of emitted audio signals at Raphe mobile device, whereinthe plurality of audio signals are generated from a plurality of lightsources using the photoacoustic effect at a plurality of knownlocations.
 10. An apparatus as claimed in claim 9, wherein the pluralityof light sources are synchronised over a network.
 11. A methodcomprising: obtaining an emitting time of at least one audio signal,wherein the at least one audio signal is generated with a photoacousticeffect; obtaining a time of arrival of the emitted at least one audiosignal in relation to a mobile device, wherein the emitted at least oneaudio signal is captured at the mobile device; and estimating a locationof the mobile device based on the emitting time and the time of arrival.12. (canceled)
 13. A mobile apparatus comprising at least one processor;and at least one memory including computer program code, the at leastone memory and the computer program code configured to, with the atleast one processor, cause the mobile apparatus at least to: detect atleast one emitted audio signal wherein the at least one audio signal isgenerated with a photoacoustic effect at a known location; and enablethe detected emitted at least one audio signal be used to estimate alocation of the mobile apparatus. 14-22. (canceled)
 23. A method asclaimed in claim 11, wherein the at least one audio signal is generatedwith the photoacoustic effect by at least one light source at a knownlocation.
 24. A method as claimed in claim 23, wherein the at least onelight source comprises a coating of photoacoustic material provided, atleast partially, around the light source.
 25. A method as claimed inclaim 23, wherein the at least one light source is coupled to amodulator for modulating intensity of light emitted by the light source.26. A method as claimed in claim 11, wherein the at least one audiosignal comprises at least one of: a predetermined waveform; or afrequency outside a threshold of human hearing.
 27. A method as claimedin claim 23, further comprising detecting a light signal, wherein thelight signal is generated from the at least one light source.
 28. Amethod as claimed in claim 27, further comprising synchronising timingbetween an apparatus that generated the at least one audio signal andthe at least one light source by using the light signal.
 29. A method asclaimed in claim 11, further comprising obtaining the time of arrival ofa plurality of emitted audio signals at the mobile device, wherein theplurality of audio signals are generated from a plurality of lightsources using the photoacoustic effect at a plurality of knownlocations.
 30. A method comprising: detecting, by a mobile apparatus, atleast one emitted audio signal wherein the at least one audio signal isgenerated with a photoacoustic effect at a known location; and enablingthe detected emitted at least one audio signal to be used to estimate alocation of the mobile apparatus.